linux-kernel - Re: [PATCH] null_blk: fix wrong capacity when bs is not 512 bytes

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Date:	Wed, 2 Sep 2015 12:42:33 -0600
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	Matias Bjørling <m@...rling.me>
Cc:	axboe@...com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] null_blk: fix wrong capacity when bs is not 512 bytes

On Mon, Aug 31, 2015 at 02:17:31PM +0200, Matias Bjørling wrote:
> set_capacity() sets device's capacity using 512 bytes sectors.
> null_blk calculates the number of sectors by size / bs, which
> set_capacity is called with. This led to null_blk exposing the
> wrong number of sectors when bs is not 512 bytes.
> 
> Signed-off-by: Matias Bjørling <m@...rling.me>
> ---
>  drivers/block/null_blk.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
> index 6f9b753..bf8f764 100644
> --- a/drivers/block/null_blk.c
> +++ b/drivers/block/null_blk.c
> @@ -588,8 +588,7 @@ static int null_add_dev(void)
>  	blk_queue_physical_block_size(nullb->q, bs);
>  
>  	size = gb * 1024 * 1024 * 1024ULL;
> -	sector_div(size, bs);
> -	set_capacity(disk, size);
> +	set_capacity(disk, size >> 9);
>  
>  	disk->flags |= GENHD_FL_EXT_DEVT | GENHD_FL_SUPPRESS_PARTITION_INFO;
>  	disk->major		= null_major;

Looks correct.

Reviewed-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
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